1. Field of the Invention
The invention relates to an adapter for fastening a filter element in a cylindrical receiving opening of a bottom part of a lower piece of a filter housing. The adapter has at least one seal that is arranged in a peripheral groove on the circumference of the adapter in order to permit fluid-tight separation of a non-filtrate chamber, which surrounds the external jacket of the filter and from which medium to be filtered can be delivered to the filter, from a filtrate chamber into which the filtrate can be introduced from the filter.
2. Description of the Related Art
DE 33 35 938 C1 discloses a multi-part filter housing for pressure filtration of fluids, having a housing top, and having a housing bottom with a housing base which has cylindrical openings, for receiving filter candles or filter elements via the adapters thereof, and separates a non-filtrate chamber surrounding the external jacket of the filter candle from a filtrate chamber via which the filter candles are each connected to a central outlet. The filter candles have, at their lower end in the vertical direction, a fluid-tight annular end cap with a central outlet connected to the tubular adapter via which the filter candle is inserted into the cylindrical opening of the housing bottom. The filter candle is located with its fluid-permeable external jacket in the non-filtrate chamber, and the annular end cap with its upper edge directed away from the housing bottom forms a fluid-tight transition area to the external jacket. To seal the adapter in the cylindrical opening of the housing bottom, the known adapter has two parallel peripheral grooves, in each of which an O-ring is arranged as a seal.
A disadvantage that has been found in principle in the known adapter is that the O-rings or cord seals have to be mounted separately. This can mean incorrect seals being fitted, at least by the user, or one of the seals being omitted.
DE 43 25 997 A1 discloses an adapter for fastening a filter element on a liquid discharge nozzle. On its inner wall directed toward the liquid discharge nozzle, the adapter has a peripheral groove with a seal arranged therein for fluid-tight separation of a non-filtrate chamber, which surrounds the external jacket of the filter and from which medium to be filtered can be delivered to the filter after filtration. The seal is at a distance from at least one side wall delimiting the base surface of the groove.
According to the teaching of DE 43 25 997 A1, a reliable seal is provided by the liquid that is to be filtered and that flows through the liquid filter, because this liquid, as a result of the pressure difference arising when it flows through the filter insert, pushes the sealing ring inside the groove in the direction toward the part of the liquid filter with the lower liquid pressure. In this way, during operation of the liquid filter or the filter element, the sealing ring or the seal is pressed onto the liquid discharge nozzle and onto a boundary surface of the groove adjacent thereto, such that a seal is ensured here despite the low or even non-existent elastic pretensioning of the sealing ring or seal.
In the device from DE 43 25 997 A1, it is always necessary that fluid to be filtered flows through the annular gap into the groove in order to ensure that the sealing ring or the seal is pressed upward into the abutment position on the end disk part, as only then is a seal achieved.
DE 20 2006 014 784 U1 discloses an annular filter insert in which an end disk covering the end of the filter body is formed in one piece by a perforated disk and a collar arranged on the latter. The collar has an axial support surface and a radial support surface. A radial sealing ring with pockets for removal of thermal energy can be applied to these support surfaces in a two-component process or by injection molding. This radial sealing ring is only limited at the bottom by the axial support surface and at the sides by the radial support surface, whereas it is open in the filtrate outflow direction. The radial sealing ring is formed integrally on the collar of the end disk, i.e. on the inner circumference of the adapter.
The radial sealing ring is quite complicated to produce because of the hollow pockets, and defects in the radial sealing ring during production thereof can be detected optically only with difficulty, particularly if the material webs or the bottom of the hollow pockets breaks and leaks occur there as a result.
Moreover, EP 1 156 538 B1 discloses a plug arrangement for closing a cell vent of a storage battery in a gas-tight manner. A closure plug has, on its circumference, a groove with an annular seal formed integrally thereon. The annular seal was molded on in a two-component injection molding process. The groove is filled completely by the annular seal.
Moreover, DE 10 2005 033 665 A1 discloses a receiving part for a plug, which receiving part has, in an inner peripheral groove, an injection-molded seal. Here too, the groove is filled completely by the sealing material.
A disadvantage of completely filling a groove with the material of the seal is that the clearance necessary for the volume deformation has to be created outside the groove.
A particular disadvantage is that the tolerances between adapter and receiving opening have to be changed in order to create a clearance for the volume deformation.
Moreover, DE 44 22 842 C1 discloses a device with a housing having at least two individual parts fitted together with the use of elastic sealing material so as to be liquid-tight. At least one of the individual parts comprises two material components, one of which is the sealing material and provides a seal, in which at most one of these two material components is bonded as a pre-molding or insert in an injection mold with the sealing material by spraying, or both components are sprayed together in a two-component injection mold, that is to say an injection mold with two cavities.
The object of the present invention is therefore to improve the known adapter for fastening a filter element in a cylindrical receiving opening of a bottom part such that it is possible to avoid fitting the seal separately. Moreover, a change in the tolerances between adapter and receiving opening should as far as possible be avoided, in order to permit the use of new adapters and also of old and known adapters in already existing receiving openings.